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MD3001 > Physiology 3 - Cardiac Contractility > Flashcards

Physiology 3 - Cardiac Contractility Flashcards

1
Q

In cardiac muscle, what does troponin bind to?

A

Tropomyosin

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2
Q

With regard to calcium, how does muscle relaxation occur?

A

Calcium is repackaged away, either in the sarcoplasmic reticulum or exchanged for sodium, which is in turn pumped out via the sodium potassium pump

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3
Q

By implementing sympathetic innervation as opposed to parasympathetic innervation, what is the effect on the ventricles?

A

Tension (not volume) increases and quicker

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4
Q

During what period is it possible to depolarise the membrane again?

A

Relative Refractory Period

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5
Q

Look at slide 5

A

Look at slide 5!

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6
Q

Why does the volume of the ventricles never go down to 0?

A

Allows for room to move - by having a 50ml reserve of blood in the ventricle, it means relaxation and contraction is a lot smoother - not having to contest with suction

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7
Q

What occurs during (normal) systole?

A

Ventricular contraction

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8
Q

What occurs during (normal) diastole?

A

Ventricular relaxation

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9
Q

11:49

A

Isovolumetric

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10
Q

When will the aortic valve open?

A

When the pressure in the ventricle exceeds the pressure in the aorta

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11
Q

Why is there a small jump in the aortic pressure just as it starts to decrease?

A

As the aortic valve closes, there is a slight rebound of blood against the valve, briefly pushing the pressure up

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12
Q

How is the stroke volume (SV) measured/calculated?

A

End diastolic volume - End systolic volume

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13
Q

How is the cardiac output (CO) calculated (L/min)

A

Stroke Volume x Heart Rate

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14
Q

During cardiac contraction, what type of ion channels does an action potential cause to open?

A

L type DHP channels

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15
Q

What is the result of L type DHP channels opening?

A

Large Ca2+ influx

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16
Q

Which type of T-tubule (cardiac or skeletal muscle) is larger and by how much?

A

Cardiac is larger - 5x greater in diameter and 25x greater in volume

17
Q

What does DHPR activation cause?

A

Release of Ca2+ from SR via RyR channels

18
Q

What is the preload?

A

How much blood is in the heart before it contracts

19
Q

What increase the preload?

A

Increased venous return

20
Q

What is responsible for the cardiac muscle refractory period?

A

Inactivation of Na+ channels

21
Q

How does cardiac muscle’s period of contraction differ to skeletal muscle’s period of contraction?

A

250ms long, as opposed to 200ms long

22
Q

Name the three ‘periods’ of cardiac contraction.

A

Absolute refractory period
Relative refractory period
Period of supranormal excitability

23
Q

What is the average duration of the ARP?

A

245ms

24
Q

At each of these contraction periods, can the cardiac muscle cells be stimulated to depolarise again and if so, how easily is this depolarisation achieved?

A

ARP - cannot be stimulated
RRP - may be stimulated, but stimulus would have to be larger than the original
SNP - smaller than normal stimulus will result in depolarisation

25
Q

What is the period of isovolumetric contraction?

A

Brief period when aortic and mitral valves are both closed, but ventricle is contracting, allowing pressure to build up to that of the aortic pressure

26
Q

What is the period of isovolumetric relaxation?

A

Period when the aortic and mitral valves are both closed and the ventricular pressure is falling, but not below that of the pressure in the atria

27
Q

What are the 4 stages of ventricular contraction/pumping?

A
  1. Isovolumetric contraction
  2. Period of rapid ejection (1/3rd of the time) - 70% of ejection fraction
  3. Period of slow ejection (2/3rds of the time) - 30% of ejection fraction
  4. Isovolumetric relaxation
28
Q

What is the average/normal aortic pressure?

A

120/80mmHg

29
Q

What is the average/normal pulmonary pressure?

A

30/12mmHg

30
Q

What is the End Systolic Volume?

A

Volume in ventricle at the end of systole (80% + 20%)

31
Q

What is the End Diastolic Volume?

A

Volume in ventricle at the end of diastole

32
Q

What is the Stroke Volume?

A

The quantity of blood expelled per beat. EDV – ESV.

33
Q

What is the Cardiac Output?

A

The volume of blood pumped by the heart over a given time period (L/min). HR x SV.

34
Q

What is normal, resting CO?

A

5L/min

MD3001 (63 decks)

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